CHESTThought Leader BlogWhen Is a Peripheral Arterial Catheter (A-Line) Indicated in My ICU Patient?

When Is a Peripheral Arterial Catheter (A-Line) Indicated in My ICU Patient?

By: Sam Zarbiv, MD and Margaret Pisani, MD, MS, FCCP

Data suggest that approximately one-third of ICU patients in the United States receive an A-line.1 Indications for placement of arterial lines include: (1) continuous beat-to-beat monitoring of blood pressure in hemodynamically unstable patients, (2) frequent sampling of blood for laboratory analysis, and (3) timing of intra-aortic balloon pump with the cardiac cycle.2 

The European Society of Intensive Care Medicine (ESICM) recommends placing an arterial line if the patient is unresponsive to therapy and/or requires vasopressors, but this is a “best practice point” based on a panel recommendation.3 The Society of Critical Care Medicine (SCCM) in their Surviving Sepsis Campaign offers a “weak recommendation,” based on very low-quality evidence that an arterial line be placed in patients requiring vasopressors.4 These recommendations are due to the lack of studies for a technology that is used with a high frequency on a daily basis in ICUs.

So how does one answer the question of when to place an arterial line in critically ill patients? Arterial line catheterization is generally considered to be a safe procedure with few serious complications and a major complication rate ranging between 1% and 5%.2 There are very few absolute contraindications to placement of an A-line, and they include an absent pulse, burns over the cannulation site, inadequate circulation to the extremity, and Raynaud’s syndrome. The majority of arterial catheters are placed in radial or femoral arteries with the radial artery being the preferred site due to lower risk of severe complications of ischemia, bleeding, and infection.

In critically ill and hemodynamically unstable patients, noninvasive blood pressure monitoring techniques may underestimate blood pressure; thus, the more intensive blood pressure monitoring via arterial catheterization may be beneficial.5 Technological advances in contemporary design of catheter and monitoring systems now allow arterial lines to be used for more advanced hemodynamic monitoring, including real-time calculation of cardiac output, stroke volume, and evaluation of fluid responsiveness in suspected hypovolemic states. Ultimately, the beat-to-beat hemodynamic information provided by arterial line catheterization is only as valuable as the intensivist’s interpretation of these data. 

A retrospective cohort did not demonstrate any improvement in mortality and there was an increased length of stay in patients with A-lines.6 Since this is this is a retrospective study, one needs to be concerned about unmeasured confounders, especially indication bias. A propensity-matched cohort analysis using the Project IMPACT database also was unable to demonstrate a benefit with the use of A-lines in mechanically ventilated patients.7

There are other downsides to arterial lines. Studies have identified artifacts in A-line derived blood pressure measurements that result in both over and underestimation of values.8,9 One needs to be aware that there may be discrepancies between radial and femoral artery measurements as demonstrated in patients with shock and hypothermia who had simultaneous measurements. Femoral mean arterial pressure (MAP) readings were found to be significantly higher than radial MAP readings in 15 (63%) of the patients in the study.10 

Despite widespread use of arterial lines for decades, there is no evidence that using them improves outcomes in the ICU. Garland in a commentary calls for rigorous controlled trials of A-lines in the ICU.11 Physicians often use A-lines because they make us feel comfortable, but our clinical practice patterns are based on what we have been taught during training and are too often based on expert opinion rather than evidence based.


  1. Gershengorn HB, Garland A, Kramer A, Scales DC, Rubenfeld G, Wunsch H. Variation of arterial and central venous catheter use in United States intensive care units. Anesthesiology. 2014;120(3):650-664.
  2. Cousins TR, O'Donnell JM. Arterial cannulation: a critical review. AANA J. 2004;72(4):267-271.
  3. Cecconi M, De Backer D, Antonelli M, et al. Consensus on circulatory shock and hemodynamic monitoring. Task force of the European Society of Intensive Care Medicine. Intensive Care Med. 2014;40(12):1795-1815.
  4. Rhodes A, Evans LE, Alhazzani W, et al. Surviving Sepsis Campaign: International Guidelines for Management of Sepsis and Septic Shock: 2016. Intensive Care Med. 2017;43(3):304-377.
  5. Shiver S, Blaivas M, Lyon M. A prospective comparison of ultrasound-guided and blindly placed radial arterial catheters. Acad Emerg Med. 2006;13(12):1275-1279.
  6. Hsu DJ, Feng M, Kothari R, Zhou H, Chen KP, Celi LA. The Association Between Indwelling Arterial Catheters and Mortality in Hemodynamically Stable Patients With Respiratory Failure: A Propensity Score Analysis. Chest. 2015;148(6):1470-1476.
  7. Gershengorn HB, Wunsch H, Scales DC, Zarychanski R, Rubenfeld G, Garland A. Association between arterial catheter use and hospital mortality in intensive care units. JAMA Intern Med. 2014;174(11):1746-1754.
  8. Dorman T, Breslow MJ, Lipsett PA, et al. Radial artery pressure monitoring underestimates central arterial pressure during vasopressor therapy in critically ill surgical patients. Crit Care Med. 1998;26(10):1646-1649.
  9. Kleinman B. Understanding natural frequency and damping and how they relate to the measurement of blood pressure. J Clin Monit. 1989;5(2):137-147.
  10. Galluccio ST, Chapman MJ, Finnis ME. Femoral-radial arterial pressure gradients in critically ill patients. Crit Care Resusc. 2009;11(1):34-38.
  11. Garland A. Arterial lines in the ICU: a call for rigorous controlled trials. Chest. 2014;146(5):1155-1158.